This invention relates to a color film inspection system for evaluating color original images before printing process and its data output method, and more particularly to a color film inspection system which converts the color and density of a film into video signals in order to evaluate a film and determine printing condition thereof and displays them on a color monitor for evaluating the color original images before printing process and the data output method therefor.
One of the conventional art color film inspection systems is disclosed in "An Instantaneous Electronic Color-Film Analyzer" (Journal of the SMPTE, 67 pp 17-26, 1958). The disclosed structure is shown in FIG. 1 wherein a negative film 31 is illuminated with a flying spot scanner (FSS) 30, and images on the negative film 31 are color-separated via dichroic mirrors DC1 and DC2 and detected by photosensors 32R, 32G and 32B of three primary colors R (red), G (green) and B (blue). The signals detected by the photosensors 32R, 32G and 32B are respectively amplified and adjusted in gain by amplifiers 33R, 33G and 33B, inputted to a gradation correction circuit 34, and then to a matrix circuit 35 for correcting undesirable pigment absorption, and sent through an exponential amplifier 36 to display the picture images of the negative film 31 on a color monitor 37. Another inspection system is proposed in "SMPTE Journal, March 1983, pp 303-307". In the inspection system shown in FIG. 2, a negative film 41 is illuminated similarily with an FSS 40 and image signals detected by photo-multipliers 42R, 42G and 42B are converted at a logarithmic converting circuit 44 via amplifier 43 into density signals, inputted to a color 48 via a masking matrix 45, a .gamma.-amplifier 46, and an exponential amplifier 47 and the picture images of the negative film 41 are displayed on a color monitor 48. In this case, the masking matrix 45 corrects the differences in detected density of the negative film due to differences between the spectral characteristics of the photographic material and that of the inspection system.
In the conventional art systems as shown in FIGS. 1 and 2, asince colors are matched by adjusting gains at amplifiers of three colors for each color, the S/N (signal/noise) ratio tends to be deteriorated as the density of the negative film increases. Unless computation of masking matrix is remade, the correction in gain by the amplifiers cannot accurately to converted to exposure on a color paper (photographic paper) or a color positive film. This is not taken into account in the prior art systems due to complexity.
Moreover, since the price of a TV (television) camera has been cut down significantly in recent years, it is noted that the combination of a white light source and a TV camera becomes cheaper than that of a flying spot scanner and photo-multipliers.
The film inspection method by the conventional systems is conducted in the procedure as shown in FIG. 3. A film with original images to be printed, for instance a negative film 100 is illuminated with light from a light source 101 and the whole images are picked up by an image pickup device such as a TV camera 102 and inputted into an image processing circuit 110. The image processing circuit 110 includes a color correction circuit, a gradation conversion table and a negative/positive converter, so that it conducts necessary processing on the video signals from the TV camera 102 to display images of the negative film 100 on a display unit 115 such as CRT via a display control circuit 113. An operator watches the images displayed on the display unit 115 and if he judges the color balance or the density unsatisfactory, corrects the images by manipulating a keyboard 114. The analyzed data of the image processing is printed out on a paper by a data output device 111 or outputted to a magnetic tape or a floppy disc. The negative film 100 which has been inspected and corrected in this way is sent to a photographic color printer 120 together with the data recorded on a recording medium 112 by the data output device 111 and the color printer 120 prints the images on a color paper to provide a photograph 121.
In the above described prior art systems, the negative film 100 on the display unit 115 is inspected by an operator, but the images on the resultant photograph 121 is printed by the photographic color printer 120 on the color paper. Unless the images displayed on the display unit 115 in the inspection system is accurately corresponded to the photograph 121 printed by the photographic color printer 120, the photograph 121 printed by the photographic color printer 120 is not necessarily optimum even if the images are correctly displayed and corrected optimally at the display unit 115. This presents a difficulty.
When an exposure density is converted into an exposure time for each of RGB colors of the photographic color printer 120, if color the printer 120 is of cut-filter type having a leak characteristic, the exposure time of RGB will not be proportional to the exposure density as it is. Moreover, the exposure density electrically obtained does not correspond to the printing density as it does not take into account the reciprocity law failure. This leads to a problem in finished gradation such as slope characteristic as they are not fully inspected on a display unit. Further, this method allows difference caused by the preference particular to a laboratory.